Video code processing method, which can generate continuous moving pictures

ABSTRACT

A video code processing method includes (a), (b), (c) and (d). The (a) step includes providing a first original bit stream including a video code which is a digitized video signal. The (b) step includes generating a second original bit stream at a first timing by delaying the first original bit stream by a specific time interval. The (c) step includes generating a converted bit stream at a second timing. The first original bit stream is code-converted into the converted bit stream. The (d) step includes switching between the second original bit stream and the converted bit stream to output. The specific time interval is adjusted such that the first timing is substantially equal to the second timing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for processing avideo code, which can receive, as a original bit stream, a bit streamconstituted by a video code, which is a digitized video signal, and thenoutput any one of the original bit stream and a converted bit streaminto which the original bit stream is code-converted. More particularly,the present invention relates to a method and apparatus for processing avideo code, which can switch smoothly without disturbing a decodedpicture when switching between the original bit stream and the convertedbit stream.

2. Description of the Related Art

Conventionally, in this method for processing a video code, when apicture data serving as a video signal is encoded to generate a bitstream, a transcoding for converting a rate of the bit stream into alower rate is carried out in order to reduce a band of a transmissionpath or a memory capacity.

For example, in a case of a standard type MPEG2 to compress or expand acolor moving picture, a bit stream is transmitted as a transport streamfrom a transmission side through an antenna or a network to a receptionside. If a band of the antenna or the network is low, the transmissionside converts the transport stream into another transport stream of alower rate. That is, the transmission is done after the execution of thetranscoding.

When the reception side records the transport stream, there may be thelimitations, such as an upper limit of a bit rate caused by a recorderor a record medium, an upper limit of a capacity and the like. Theperformance as a memory capacity of a recorder can be improved if thetransport stream is converted into the transport stream of the lowerrate when it is recorded, namely, if it is recorded after the executionof the transcoding.

Although there may be various methods for the transcoding, it can beattained by a combination of a decoder and an encoder as a simplemethod. In short, a bit stream is inputted to the decoder, andcompletely decoded. An output picture data is inputted to the encoder tothen generate and output a bit stream of a desirable rate. However, thismethod carries out the processes for decoding and encoding the bitstream. Thus, the output bit stream is more delayed than the input bitstream by a time necessary for the respective decoding and encodingprocesses.

For example, in a case of a compression method using a correlationbetween frames such as the MPEG2, a time delay is induced because of arearrangement of the frames. That is, a bidirectionally predictiveencode picture (B picture) is accumulated in the bit stream in an orderdifferent from a picture display order. In a case of a typical MPEG2stream of [M=3], when the decoding process is done, it brings about adelay corresponding to three frames. Moreover, even when the encodingprocess is done, it brings about a delay corresponding to three framessince it waits for an intra encode picture (I-picture) and a predictiveencode picture (P-picture).

That is, the bit stream on which the transcoding is performed has thedelay corresponding to six frames with respect to the input original bitstream. For this reason, the simply switching operation between theoriginal bit stream and the bit stream on which the transcoding isperformed causes the moving picture to be discontinuous. Switchingbetween them by omitting the rearrangement of the frames so as not tobring about the time delay results in the disturbance of a screen sincethe decoding and encoding processes are not carried out normally.

Here, the method for perfectly decoding by using the decoder has beenalready described as the method for the transcoding. However, as anotherattaining method, for example, even a method for decoding up to a DCT(Discrete Cosine Transformation) area and again encoding and the likebring about the situation similar to the above-mentioned situation sincethe bit stream on which the transcoding is performed has the delay withrespect to the original bit stream.

Conventionally, there are the proposals of the techniques with regard toa buffer control and a rate control of a bit stream itself on which thetranscoding is performed. However, there is no information correspondingto a control with regard to a time difference between the original bitstream and the bit stream on which the transcoding is performed.

The above-mentioned conventional method and system for processing thevideo code have the problem that they can not generate the continuousmoving pictures when switching from the bit stream on which thetranscoding is performed to the original bit stream, or from theoriginal bit stream to the bit stream on which the transcoding isperformed, in the course of the bit stream.

This is because the bit stream on which the transcoding is performed hasthe delay corresponding to the time necessary for the transcodingprocess as compared with the original bit stream. Also, this is becausethe simply switching operation can not be done because of the differenceof the bit stream structure caused by the encoding structure.

SUMMARY OF THE INVENTION

The present invention is accomplished in view of the above mentionedproblems. Therefore, an object of the present invention is to provide amethod and system for processing a video code, which can generatecontinuous moving pictures even when switching from a bit stream onwhich a transcoding is performed to an original bit stream, or from theoriginal bit stream to the bit stream on which the transcoding isperformed, in a course of the bit streams.

In order to achieve an aspect of the present invention, a video codeprocessing method, includes: (a) providing a first original bit streamincluding a video code which is a digitized video signal; (b) generatinga second original bit stream at a first timing by delaying the firstoriginal bit stream by a specific time interval; (c) generating aconverted bit stream at a second timing, the first original bit streambeing code-converted into the converted bit stream; and (d) switchingbetween the second original bit stream and the converted bit stream tooutput, and wherein the specific time interval is adjusted such that thefirst timing is substantially equal to the second timing.

In this case, the specific time interval is adjusted such thatcontinuous moving pictures corresponding to the first original bitstream can be obtained even when the (d) is performed in a course of thesecond original bit stream and the converted bit stream.

Also in this case, each of the second original bit stream and theconverted bit stream has a plurality of frames, and wherein the (d)includes switching between the second original bit stream and theconverted bit stream at a switching point corresponding to a startposition or end position of one of the plurality of frames of the secondoriginal bit stream and the converted bit stream.

Further in this case, the first timing is determined by monitoring thesecond timing and controlling the specific time interval based on themonitoring result.

In this case, the first timing is determined by monitoring the first andsecond timings and controlling the specific time interval based on themonitoring result.

Also in this case, the first timing is determined by monitoring thefirst and second timings and performing feedback control on the specifictime interval such that a difference between the first and secondtimings is reduced based on the monitoring result.

Further in this case, the (d) includes switching between the secondoriginal bit stream and the converted bit stream at a switching pointdetected in accordance with a bit stream structure of an encoded pictureof the first original bit stream.

In this case, the switching point is detected in accordance with a bitstream structure of an encoded picture of the first original bit streamsuch that continuous moving pictures corresponding to the first originalbit stream can be obtained without a disturbance in the continuousmoving pictures.

Also in this case, a video code processing method, further includes: (f)inputting a switch command at a third timing, and wherein each of thesecond original bit stream and the converted bit stream corresponds toMPEG (Moving Picture Experts Group) 2 type and has a plurality of GOPs(Group of Picture), each of the plurality of GOPs including anIntra-Picture (I Picture), a Predictive-Picture (P picture) and aBidirectionally predictive-Picture (B picture), and wherein the (d)includes switching between the second original bit stream and theconverted bit stream at a switching point corresponding to a leadposition of one of the plurality of GOPs which is on the third timing orthe closest to the third timing after the third timing.

In order to achieve another aspect of the present invention, a videocode processing apparatus, includes: a buffer section inputting a firstoriginal bit stream including a video code which is a digitized videosignal to generate a second original bit stream at a first timing bydelaying the first original bit stream by a specific time interval; atranscoding section generating a converted bit stream at a secondtiming, the first original bit stream being code-converted into theconverted bit stream; and a switching section switching between thesecond original bit stream and the converted bit stream to output, andwherein the specific time interval is adjusted such that the firsttiming is substantially equal to the second timing.

In this case, the specific time interval is adjusted such thatcontinuous moving pictures corresponding to the first original bitstream can be obtained even when the switching section switches betweenthe second original bit stream and the converted bit stream in a courseof the second original bit stream and the converted bit stream.

Also in this case, each of the second original bit stream and theconverted bit stream has a plurality of frames, and wherein theswitching section switches between the second original bit stream andthe converted bit stream at a switching point corresponding to a startposition or end position of one of the plurality of frames of the secondoriginal bit stream and the converted bit stream.

Further in this case, a video code processing apparatus, furtherincludes: a buffer controlling section monitoring the second timing tocontrol the specific time interval based on the monitoring result.

In this case, a video code processing apparatus, further includes: abuffer controlling section monitoring the first and second timings tocontrol the specific time interval based on the monitoring result.

Also in this case, a video code processing apparatus, further includes:a buffer controlling section monitoring the first and second timings toperform feedback control on the specific time interval such that adifference between the first and second timings is reduced based on themonitoring result.

Further in this case, the switching section switches between the secondoriginal bit stream and the converted bit stream at a switching pointdetected in accordance with a bit stream structure of an encoded pictureof the first original bit stream.

In this case, a video code processing apparatus, further includes: aswitch controlling section inputting a switch command at a third timingto determine a switching point at which the switching section switchesbetween the second original bit stream and the converted bit stream, andwherein each of the second original bit stream and the converted bitstream corresponds to MPEG (Moving Picture Experts Group) 2 type and hasa plurality of GOPs (Group of Picture), each of the plurality of GOPsincluding an Intra-Picture (I Picture), a Predictive-Picture (P picture)and a Bidirectionally predictive-Picture (B picture), and wherein theswitch controlling section determines the switching point such that theswitching point corresponds to a lead position of one of the pluralityof GOPs which is on the third timing or the closest to the third timingafter the third timing.

Also in this case, the buffer section and the transcoding section andthe switching section are included in a single unit.

Further in this case, the buffer section and the transcoding section andthe switching section and the buffer controlling section are included ina single unit.

In this case, the buffer section and the transcoding section and theswitching section and the buffer controlling section and the switchcontrolling section are included in a single unit.

It is possible to output an encoded data in which screens of movingpictures are coincident since such a device tentatively holds therein aninput original bit stream and then makes a timing of the input originalbit stream coincide with a timing of an output of a bit stream on whicha transcoding is performed.

Moreover, since a switching controller is included, it is possible toaccurately treat an encoded data corresponding to the same screen of amoving picture even for a bit stream structure of a different kind of anencode picture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a function block diagram showing an embodiment of the presentinvention;

FIG. 2A is a timing chart showing a original bit stream inputted to atranscoder of FIG. 1;

FIG. 2B is a timing chart showing a converted bit stream outputted bythe transcoder of FIG. 1;

FIG. 2C is a timing chart showing a original bit stream outputted by abuffer of FIG. 1;

FIG. 3 is a function block diagram showing an embodiment of the presentinvention, differently from FIG. 1;

FIG. 4A is a timing chart showing a original bit stream inputted to atranscoder of FIG. 3;

FIG. 4B is a timing chart showing a converted bit stream outputted bythe transcoder of FIG. 3;

FIG. 4C is a timing chart showing a command outputted by a buffercontroller of FIG. 3;

FIG. 4D is a timing chart showing a original bit stream outputted by thebuffer of FIG. 3;

FIG. 5A is a timing chart showing a raw or converted bit stream of FIG.3;

FIG. 5B is a timing chart showing a switch command inputted to theswitch controller of FIG. 3; and

FIG. 5C is a timing chart showing a switch command outputted by theswitch controller of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below withreference to the attached drawings.

FIG. 1 is a function block diagram showing an embodiment of the presentinvention. It is provided with a transcoder 1 and a buffer 2 forreceiving a original bit stream to be inputted, and a switcher 3 forswitching any one of outputs of the transcoder 1 and the buffer 2 andthen connecting it to an external portion.

FIG. 1 is different from the conventional system for processing a videocode, in a fact that the buffer 2 is mounted.

The transcoder 1 inputs the original bit stream A to convert into aconverted bit stream B of a low rate, and outputs to the switcher 3. Thebuffer 2 inputs the original bit stream A to hold therein only for aperiod of the conversion in the transcoder 1, and outputs to theswitcher 3. The switcher 3 switches between the converted bit stream Boutputted by the transcoder 1 and the original bit stream A outputted bythe buffer 2, based on a switch command from the external portion, andoutputs any one of the bit streams A, B to the external portion.

The operations of the function block in FIG. 1 will be described belowwith reference to FIGS. 1 and 2A to 2C. FIG. 2A is a timing chartshowing the original bit stream A inputted to the transcoder 1. FIG. 2Bis a timing chart showing the converted bit stream B outputted by thetranscoder 1. And, FIG. 2C is a timing chart showing the original bitstream A outputted by the buffer 2.

The converted bit stream B outputted by the transcoder 1 has a delaycorresponding to a process time tp in the transcoder 1, as compared withthe original bit stream A inputted to the transcoder 1, as shown inFIGS. 2A and 2B.

As shown in FIGS. 2A and 2C, the buffer 2 holds therein the original bitstream A inputted to the transcoder 1 only for the process time tp, andoutputs it. Thus, in input sections of the switcher 3, respective framepositions of the converted bit stream B outputted by the transcoder 1and the original bit stream A outputted by the buffer 2 are in temporalcoincidence with each other. The switcher 3 switches between the twoinput signals, namely, between the converted bit stream B on which thetranscoding is performed and the original bit stream A outputted by thebuffer 2, at a point such as a frame start or a frame end. As a result,it is possible to switch between the encode data without a disturbancein a moving picture.

An embodiment different from that of FIG. 1 will be described below withreference to FIG. 3. In FIG. 3, a system is provided with a transcoder11, a buffer 12, a switcher 13, a buffer controller 14 and a switchcontroller 15.

FIG. 3 is different from FIG. 1 in a fact that the buffer controller 14for controlling the buffer 12 and the switch controller 15 forcontrolling the switcher 13 are added.

The transcoder 11 has the function equal to the conventional function ofconverting the original bit stream A into the converted bit stream B ofthe low rate. The transcoder 11 outputs the converted bit stream B tothe switcher 13, the buffer controller 14 and the switch controller 15.

The buffer 12 tentatively holds therein the original bit stream A underthe control of the buffer controller 14, and outputs to the switcher 13,the buffer controller 14 and the switch controller 15.

The switcher 13 receives the converted bit stream B outputted by thetranscoder 11 and the original bit stream A outputted by the buffer 12,switches between the converted bit stream B and the original bit streamA, at a switch point between the frames, under the control of the switchcontroller 15, and outputs any one of the bit streams A, B to anexternal portion.

The buffer controller 14 receives the converted bit stream B from thetranscoder 11 and the original bit stream A from the buffer 12. Based onthe input signals A, B, the buffer controller 14 controls the buffer 12so that the original bit stream A outputted by the buffer 12 istemporally equal to the converted bit stream B outputted by thetranscoder 11 at the switch point between the frames.

The switch controller 15 receives the converted bit stream B outputtedby the transcoder 11 or the original bit stream A outputted by thebuffer 12, and controls the switcher 13 so as to switch at a timingsuitable for the bit stream structure, based on a switch commandinputted from the external portion.

The operations of the buffer controller 14 in FIG. 3 will be describedbelow with reference to FIG. 3 and FIGS. 4A to 4D.

The converted bit stream B outputted by the transcoder 11 has a delaycorresponding to a process time tp in the transcoder 11, as comparedwith the original bit stream A inputted to the transcoder 11, as shownin FIGS. 4A and 4B. The buffer 12 tentatively holds therein the originalbit stream A, to output it, based on a command of the buffer controller14 as shown in FIGS. 4C and 4D.

As shown in FIGS. 4B to 4D, the buffer controller 14 performs a controlof holding and outputting the bit stream, on the buffer 12 so that theconverted bit stream B outputted by the transcoder 11 is temporallyequal to the original bit stream A outputted by the buffer 12. Forexample, the buffer controller 14 compares the original bit stream Aoutputted by the buffer 12 with the converted bit stream B outputted bythe transcoder 11, and performs a feedback control on the buffer 12 soas to reduce a difference at a switch point between the frames to asmall value, based on the comparison result.

The operations of the switch controller 15 in FIG. 3 will be describedbelow with reference to FIG. 3 and FIGS. 5A and 5B.

The switch controller 15 controls the switcher 13 so that the bitstreams A, B are switched at an optimal timing. As the switch timingused in the switch controller 15, for example, when the bit streamscorresponds to the MPEG2, it is possible to use a unit of a group ofpictures (GOP) composed of an intra encode picture (I-picture), anpredictive encode picture (P-picture) and a bidirectionally predictiveencode picture (B-picture) (refer to FIG. 5A).

FIG. 5A is a timing chart showing the converted bit stream B or theoriginal bit stream A outputted by the buffer 12 which is received bythe switch controller 15. Since the switch controller 15 receives theoriginal bit stream A outputted by the buffer 12, an input timing of theoriginal bit stream A is equal to that of the converted bit stream B. Asmentioned above, the two timings of the bit streams A, B received by theswitch controller 15 are equal to each other. So, from the viewpointthat it may be any timing of the two bit streams A, B, FIG. 5A shows thetiming of the original bit stream A or the converted bit stream B.

As shown in FIGS. 5B and 5C, let us suppose that the switch controller15 receives the switch command of the transcoding from a user or thesystem at a point Ti. The switch controller 15 detects a lead point Tsof a first GOP (refer to FIG. 5C) on and after the point Ti of FIG. 5B,in the original bit stream A outputted by the buffer 12 or the convertedbit stream B on which the transcoding is performed as shown in FIG. 5A.Then, the switch controller 15 instructs the switcher 13 to carry outthe switching operation at the lead point Ts.

The switcher 13 will be described below by referring back to FIG. 3.

The switcher 13 switches to any one of the two input signals, namely,any one of the converted bit stream B on which the transcoding isperformed and the original bit stream A outputted by the buffer 12, andconnects it to an external output. In the MPEG2, all encoded picturescan be decoded for each the GOP. Thus, any disturbance in the decodedpictures is never induced before and after the switching operation.

As mentioned above, the shortest switch point within the frame isselected for each of the bit stream structures of different kinds ofencoded pictures. Thus, it is possible to accurately treat the encodeddata corresponding to the same screen of the dynamic image in theshortest time, for the switch command (the switch command received atthe point Ti in the above-mentioned example) from the external portion.Hence, even in any of the bit stream structures, it is possible toswitch between the original bit stream A and the converted bit stream Bwithout the disturbance in the picture in the shortest time, for theswitch command from the external portion.

Also, in the above-mentioned case, the buffer 12 and the switcher 13 areexplained as respective single members (units). However, instead of theconfiguration, the transcoder 11 can contain therein the buffer functionof the buffer 12 and the switch function of the switcher 13.

Here, the transcoder 11 containing therein the buffer functiontentatively holds therein the original bit stream A until the originalbit stream A is code-converted into the converted bit stream B, and thenoutputs the original bit stream A at the same timing as the outputtiming of the converted bit stream B.

Here, the transcoder 11 containing therein the switch function switchesbetween the converted bit stream B and the original bit stream A havingthe same timing through the buffer function, based on the switch commandfrom the external portion, and then outputs to the external portion.

The transcoder 11 containing therein the buffer function and the switchfunction as mentioned above can further contain therein the buffercontrol function of the buffer controller 14 as mentioned above. Thetranscoder 11 containing therein the buffer control function instructsthe buffer function to make the output timings of both the bit streamsB, A coincide with each other, based on the converted bit stream B andthe original bit stream A outputted by the buffer function, andaccordingly controls the tentatively held amount of the original bitstream A.

The transcoder 11 containing therein the buffer function, the switchfunction and the buffer control function as mentioned above can furthercontain therein the switch control function of the switch controller 15as mentioned above. The transcoder 11 containing therein the switchcontrol function detects the switch timing corresponding to the bitstream structure of any one encoded picture of both the bit streams B,A, based on the converted bit stream B and the original bit stream Aoutputted by the buffer function. After that, the transcoder 11, whenreceiving the switch command from the external portion, makes itcoincide with the switch timing, and instructs the switch function, andthen outputs any one of the converted bit stream B and the original bitstream A outputted by the buffer function.

In the above-mentioned explanation, the timing adjustment in the bufferis done at the frame unit, and the point of the switch control isdefined as the GOP unit. However, another suitable unit may be selecteddepending on the configuration of the bit stream.

Also, the function blocks are illustrated and described. However, it isfree to separate or merge the functions as long as the separation or themerger satisfies the above-mentioned functions. The above-mentionedexplanations do not limit the present invention.

As mentioned above, the present invention can obtain the followingeffects.

The first effect lies in the fact that the continuous dynamic images canbe generated even when switching from the bit stream on which thetranscoding is performed to the original bit stream, in the course ofthe bit streams, or switching from the original bit stream to the bitstream on which the transcoding is performed in the course of the bitstreams.

This is because it is possible to output the original bit stream at thesame timing as the bit stream on which the transcoding is performed, bymounting the buffer function in the original bit stream to be inputted.As a result, the encoded data of the same dynamic image can be connectedto the external output, even in any of the original bit stream and thebit stream on which the transcoding is performed.

The second effect lies in the fact that even in any of the bit streamstructures, the switching operation can be done without the disturbancein the picture, in the shortest time, for the switch command from theexternal portion.

This is because it is possible to switch between the bit streams byselecting the optimal switch point from the bit stream structures basedon the switch control function.

1. A video code processing method, comprising: (a) providing a firstoriginal bit stream including a video code which is a digitized videosignal; (b) generating a second original bit stream at a first timing bydelaying said first original bit stream by a specific time interval; (c)generating a converted bit stream at a second timing, said firstoriginal bit stream being code-converted into said converting bitstream; and (d) switching between said second original bit stream andsaid converted bit stream to output; (e) monitoring said second signalin bit stream and said converted bit stream; and (f) generating a delaycontrol signal response to the monitoring, wherein said specific timeinterval is adjusted by said delay control signal such that said firsttiming is substantially equal to said second timing.
 2. A video codeprocessing method according to claim 1, wherein said specific timeinterval is adjusted such that continuous moving pictures correspondingto said first original bit stream can be obtained even when said step(d) is performed in a course of said second original bit stream and saidconverted bit stream.
 3. A video code processing method according toclaim 1, wherein each of said second original bit stream and saidconverted bit stream has a plurality of frames, and wherein said step(d) includes switching between said second original bit stream and saidconverted bit stream at a switching point corresponding to a startposition or end position of one of said plurality of frames of saidsecond original bit stream and said converted bit stream.
 4. A videocode processing method according to claim 1, wherein said first timingis determined by monitoring said second timing and controlling saidspecific time interval based on the monitoring result.
 5. A video codeprocessing method according to claim 1, wherein said first timing isdetermined by monitoring said first and second timings and controllingsaid specific time interval based on the monitoring result.
 6. A videocode processing method according to claim 5, wherein said first timingis determined by monitoring said first and second timings and performingfeedback control on said specific time interval such that a differencebetween said first and second timings is reduced based on the monitoringresult.
 7. A video code processing method according to claim 1, whereinsaid step (d) includes switching between said second original bit streamand said converted bit stream at a switching point detected inaccordance with a bit stream structure of an encoded picture of saidfirst original bit stream.
 8. A video code processing method accordingto claim 7, wherein said switching point is detected in accordance witha bit stream structure of an encoded picture of said first original bitstream such that continuous moving pictures corresponding to said firstbit stream can be obtained without a disturbance in said continuousmoving pictures.
 9. A video code processing method according to claim 1,further comprising: (g) inputting a switch command at a third timing,and wherein each of said second original bit stream and said convertedbit stream corresponds to MPEG (Moving Picture Experts Group) 2 type andhas a plurality of GOPs (Group of Pictures), each of said plurality ofGOPs including an Intra-Picture (I Picture), a Predictive-Picture (Ppicture) and a Bidirectionally predictive-Picture (B picture), andwherein said step (d) includes switching between said second originalbit stream and said converted bit stream at a switching pointcorresponding to a lead position of one of said plurality of GOPs whichis on said third timing or the closest to said third timing after saidthird timing.
 10. A video code processing apparatus, comprising; abuffer section inputting a first original bit stream including a videocode which is a digitized video signal to generate a second original bitstream at a first timing by delaying said first original bit stream by aspecific time interval; a transcoding section generating a converted bitstream at a second timing, said first original bit stream beingcode-converted into said converted bit stream; and a switching secondswitching between said second original bit stream and said converted bitstream to output; and a buffer controlling section that receives asinputs said second original bit stream and said converted bit stream andoutputs a buffer control signal, wherein said specific time interval isadjusted by said buffer controller signal such that said first timing issubstantially equal to said second timing.
 11. A video code processingapparatus according to claim 10, wherein said specific time interval isadjusted such that continuous moving pictures corresponding to saidfirst original bit stream can be obtained even when said switchingsection switches between said second original bit stream and saidconverted bit stream in a course of said second original bit stream andsaid converted bit stream.
 12. A video code processing apparatusaccording to claim 11, wherein each of said second original bit streamand said converted bit stream has a plurality of frames, and whereinsaid switching section switches between said second original bit streamand said converted bit stream at a switching point corresponding to astart position or end position of one of said plurality of frames ofsaid second original bit stream and said converted bit stream.
 13. Avideo code processing apparatus according to claim 10, wherein saidbuffer controlling section monitoring said second timing to control saidspecific time interval based on the monitoring result.
 14. A video codeprocessing apparatus according to claim 10, further comprising: a buffercontrolling section monitoring said first and second timings to controlsaid specific time interval based on the monitoring result.
 15. A videocode processing apparatus according to claim 10, further comprising: abuffer controlling section monitoring said first and second timings toperform feedback control on said specific time interval such that adifference between said first and second timings is reduced based on themonitoring result.
 16. A video code processing apparatus according toclaim 10, wherein said switching section switches between said secondoriginal bit stream and said converted bit stream at a switching pointdetected in accordance with a bit stream structure of an encoded pictureof said first original bit stream.
 17. A video code processing methodaccording to claim 10, further comprising: a switch controlling sectioninputting a switch command at a third timing to determine a switchingpoint at which said switching section switches between said secondoriginal bit stream and said converted bit stream, and wherein each ofsaid second original bit stream and said converted bit streamcorresponds to MPEG (Moving Picture Experts Group) 2 type and has aplurality of GOPs (Group of Pictures), each of said plurality of GOPsincluding an Intra-Picture (I Picture), a Predictive-Picture (P picture)and a Bidirectionally predictive-Picture (B picture), and wherein saidswitch controlling section determines said switching point such thatsaid switching point corresponds to a lead position of one of saidplurality of GOPs which is on said third timing or the closest to saidthird timing after said third timing.
 18. A video code processingapparatus according to claim 10, wherein said buffer section and saidtranscoding section and said switching section are included in a singleunit.
 19. A video code processing apparatus according to claim 13,wherein said buffer section and said transcoding section and saidswitching section and said buffer controlling section are included in asingle unit.
 20. A video code processing apparatus according to claim17, wherein said buffer section and said transcoding section and saidswitching section and said buffer controlling section and said switchcontrolling section are included in a single unit.